glGetLightiv
GLGETLIGHT(3G) GLGETLIGHT(3G)
NAME
glGetLightfv, glGetLightiv - return light source parameter values
C SPECIFICATION
void glGetLightfv( GLenum light,
GLenum pname,
GLfloat *params )
void glGetLightiv( GLenum light,
GLenum pname,
GLint *params )
PARAMETERS
light Specifies a light source. The number of possible lights
depends on the implementation, but at least eight lights are
supported. They are identified by symbolic names of the form
GL_LIGHTi where 0 ≤ i < GL_MAX_LIGHTS.
pname Specifies a light source parameter for light. Accepted sym-
bolic names are GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR,
GL_POSITION, GL_SPOT_DIRECTION, GL_SPOT_EXPONENT,
GL_SPOT_CUTOFF, GL_CONSTANT_ATTENUATION,
GL_LINEAR_ATTENUATION, and GL_QUADRATIC_ATTENUATION.
params Returns the requested data.
DESCRIPTION
glGetLight returns in params the value or values of a light source
parameter. light names the light and is a symbolic name of the form
GL_LIGHTi for 0 ≤ i < GL_MAX_LIGHTS, where GL_MAX_LIGHTS is an imple-
mentation dependent constant that is greater than or equal to eight.
pname specifies one of ten light source parameters, again by symbolic
name.
The following parameters are defined:
GL_AMBIENT params returns four integer or floating-point val-
ues representing the ambient intensity of the
light source. Integer values, when requested, are
linearly mapped from the internal floating-point
representation such that 1.0 maps to the most pos-
itive representable integer value, and -1.0 maps
to the most negative representable integer value.
If the internal value is outside the range [-1,
1], the corresponding integer return value is
undefined. The initial value is (0, 0, 0, 1).
GL_DIFFUSE params returns four integer or floating-point val-
ues representing the diffuse intensity of the
light source. Integer values, when requested, are
linearly mapped from the internal floating-point
representation such that 1.0 maps to the most pos-
itive representable integer value, and -1.0 maps
to the most negative representable integer value.
If the internal value is outside the range [-1,
1], the corresponding integer return value is
undefined. The initial value for GL_LIGHT0 is (1,
1, 1, 1); for other lights, the initial value is
(0, 0, 0, 0).
GL_SPECULAR params returns four integer or floating-point val-
ues representing the specular intensity of the
light source. Integer values, when requested, are
linearly mapped from the internal floating-point
representation such that 1.0 maps to the most pos-
itive representable integer value, and -1.0 maps
to the most negative representable integer value.
If the internal value is outside the range [-1,
1], the corresponding integer return value is
undefined. The initial value for GL_LIGHT0 is (1,
1, 1, 1); for other lights, the initial value is
(0, 0, 0, 0).
GL_POSITION params returns four integer or floating-point val-
ues representing the position of the light source.
Integer values, when requested, are computed by
rounding the internal floating-point values to the
nearest integer value. The returned values are
those maintained in eye coordinates. They will
not be equal to the values specified using
glLight, unless the modelview matrix was identity
at the time glLight was called. The initial value
is (0, 0, 1, 0).
GL_SPOT_DIRECTION params returns three integer or floating-point
values representing the direction of the light
source. Integer values, when requested, are com-
puted by rounding the internal floating-point val-
ues to the nearest integer value. The returned
values are those maintained in eye coordinates.
They will not be equal to the values specified
using glLight, unless the modelview matrix was
identity at the time glLight was called. Although
spot direction is normalized before being used in
the lighting equation, the returned values are the
transformed versions of the specified values prior
to normalization. The initial value is (0, 0, -1).
GL_SPOT_EXPONENT params returns a single integer or floating-point
value representing the spot exponent of the light.
An integer value, when requested, is computed by
rounding the internal floating-point representa-
tion to the nearest integer. The initial value is
0.
GL_SPOT_CUTOFF params returns a single integer or floating-point
value representing the spot cutoff angle of the
light. An integer value, when requested, is com-
puted by rounding the internal floating-point rep-
resentation to the nearest integer. The initial
value is 180.
GL_CONSTANT_ATTENUATION
params returns a single integer or floating-point
value representing the constant (not distance-
related) attenuation of the light. An integer
value, when requested, is computed by rounding the
internal floating-point representation to the
nearest integer. The initial value is 1.
GL_LINEAR_ATTENUATION
params returns a single integer or floating-point
value representing the linear attenuation of the
light. An integer value, when requested, is com-
puted by rounding the internal floating-point rep-
resentation to the nearest integer. The initial
value is 0.
GL_QUADRATIC_ATTENUATION
params returns a single integer or floating-point
value representing the quadratic attenuation of
the light. An integer value, when requested, is
computed by rounding the internal floating-point
representation to the nearest integer. The initial
value is 0.
NOTES
It is always the case that GL_LIGHTi = GL_LIGHT0 + i.
If an error is generated, no change is made to the contents of params.
ERRORS
GL_INVALID_ENUM is generated if light or pname is not an accepted
value.
GL_INVALID_OPERATION is generated if glGetLight is executed between
the execution of glBegin and the corresponding execution of glEnd.
SEE ALSO
glLight(3G)
GLGETLIGHT(3G)
